1. Field of the Invention
The present invention relates to a structure of an induction coupling apparatus used in power line carrier communication.
2. Description of the Related Art
An induction coupling apparatus is an apparatus for superposing a data signal on a power line by electromagnetic induction. Using a magnetic core surrounding a power line and an exciting coil surrounding the magnetic gore to apply signal electric current to the exciting coil generates the electromagnetic induction. The magnetic core is arranged to be able to be divided into two. A mechanism capable of separating and uniting the magnetic core having such a structure is used for mounting the magnetic core to the power line.
In a conventional induction coupling apparatus, one side of the respective divided parts of the magnetic core having a structure divided into two is connected by means of a hinge while the other side is opened and closed, so that the magnetic core is mounted to the power line so as to surround the power line. An upper side core of the magnetic core divided into two is provided with a lifting grip and a bolt for opening and closing the core. A lower side core is provided with a bolt for fixing the upper side core (See Patent Reference 1, for example).
Patent Reference 1: JP-A-2005-525021 (FIGS. 3 and 6 and description thereof)
The conventional induction coupling apparatus disclosed in Patent Reference 1 or such, which is formed as described above, has a structure that the induction coupling apparatus can slide to move in the longitudinal direction of the power line. In the case that the induction coupling apparatus moves from a predetermined position of the power line to another position along the power line due to a blast of wind or such, a malfunction such as a defect in connection or cutting of a signal line occurs in some cases due to force added to the signal line connected to the induction coupling apparatus. Further, in the case that an ordinary wind, which is comparatively strong, blows, a respiration phenomenon of the wind that the strength of the wind varies causes repeated collision between the power line and the magnetic core whenever the strength of the wind changes since the induction coupling apparatus is arranged to slide to move in the longitudinal direction of the power line, that is, since a gap allowing the movement is formed between the power line and the magnetic core. Oscillation due to the repeated collision causes an undesirable variation in induction coupling efficiency. Moreover, the repeated collision causes damage to the power line and the magnetic core in a long term, so that the reliability is likely to decline.
In addition, the upper and lower side magnetic cores are connected with each other by means of a hinge. Such a structure may cause a difference in space between the respective magnetic cores on the upper and lower sides according to tolerance of the hinge part. Accordingly, the hinge part manufactured at a low cost with poor accuracy causes deterioration in accuracy of a space of a gap, and thereby, deterioration in induction coupling efficiency. In the case that the hinge part is manufactured with high accuracy, however, there is no problem in induction coupling efficiency but a problem that the manufacturing cost becomes high is caused.
Furthermore, angles of the grip, the opening and closing bolt and a fixing bolt are uneven. This causes a structure that the angle for connecting the lifting grip used for mounting the apparatus to the power line is uneven. Accordingly, troublesome operations are required such that the grip of the apparatus is held from the upper part by means of a handle in putting the core on the power line, the opening and closing bolt is operated from the lower part in opening and closing the core and the fixing bolt different from the opening and closing bolt is operated at another angle in fixing the core.
Therefore, in manufacturing an induction coupling apparatus used in power line carrier communication, required are research and development of a structure capable of securing satisfactory induction coupling efficiency and high reliability.